s15.2 heat engines and the second law of thermodynamics 3→4dp=0gc=nC(T4-) 0=0 T =T1p2 E=1 T-7 =1 OHT2 P≠0 E<1 s15.2 heat engines and the second law of thermodynamics (b)Otto cycle7 3 → 4 d p = 0 ( ) QC = nCp T4 −T3 4 → 1 dQ = 0 1 1 2 1 4 1 − − − − = γ γ γ γ T p T p H C Q Q ε = 1− 2 1 3 4 1 T T T T − − = − γ −γ = − 1 1 2 1 ( ) p p 0 1 Q P2 ≠ ∴ ε < §15.2 heat engines and the second law of thermodynamics (b) Otto cycle QH W QC e b c d Vf Vi V P a §15.2 heat engines and the second law of thermodynamics